Compound propulsion system



Nov. 12, 1963 T. N. EDELBAUM ETAL 3,110,154

COMPOUND PRoPuLsIoN SYSTEM Filed Feb. 6. 1961 /NvE/vToRs THEoDoD/s /v.EDEL BAUM EDWARD APM/SLU United States Patent O 3,110,154 CMPUNDPRPULSEN SYSTEM Theodore N. l'ldelhaum, Windsor, Conn., and Edward A.

linsley, Cambridge, Mass., designers to United Aircraft Gorporation,)East Hartford, Sonn., a corporation of Delaware File-d lFeb. 6, will,Ser. No. 87,394 i4- Claims. (Cl. oil-35.6)

This invention relates to a compound propulsion system and moreparticularly to a propulsion device having interrelated propulsion unitswith `one of the units being a high-thrust, short-duration device andthe other of the units being a low-thrust, high-specific impulse,long-duration device.

ln certain space missions it is desirable to obtain shortdurationimpulsive thrust for rapid maneuvering. It is also desirable to haverelatively long-duration low thrust available for efficient long-rangeoperation. Electric propulsion systems serve the latter purpose but arenot adequate for maneuvering, since the weight of the requiredelectrical generating system would be prohibitive.

lt is, therefore, a primary object of this invention to combine anelectrical propulsion device with a chemical rocket, with the chemicalrocket being utilized for short duration, high-thrust maneuveringpurposes.

It is a further object of this invention to provide a combined chemicaland electrical propulsion device with one or more of the fuels for thechemical rocket being utilized jointly in 'both propulsion devices.

These and other objects of this invention will bec me readily apparentfrom the following detailed description of the drawing which illustratesa schematic arrangement of a type of compound propulsion system of thisinvention.

Referring to the FIGURE, a fuel storage tank containing, for example,lithium, is indicated at ld. The lithium is used as a common fuel inboth the rocket propulsion unit l2 and the electric propulsion unit le.The electrical propulsion unit ld eventually obtains its power through asuitable generator (referred t lhereinafter at 54) which generator inturn receives power from a combined primary power circuit lo and asecondary power circuit l. The propulsion unit 14 is illustrated byexample as a bombardment ion engine out may readily take the form of anarc jet (which may accelerate hydrogen received from the rocket source),a magneto-hydrodynamic accelerator or other ion engine. The lithium fromthe storage tank lill is pumped by one or more pumping units Ztl and 22into the primary circuit lo through a suitable nuclear reactor Zfi. Thenuclear reactor, which may be of any well-known type, adds heat to theliquid lithium and discharges the heated lithium from a line 26.Suitable valves 28 and Sli control the llow of lithium into a heatexchanger coil 34- so that the lithium, in fact, circulates from thenuclear reactor 2d to the heat exchanger coil 34 and then back to thereactor for added heating. The heat exchanger receives flow of asuitable working liquid (for example, a liquid metal) from a pump to andan inlet line 32. This liquid flows in the secondary circuit l. Theliquid picks up heat in the heat exchanger and discharges the heatedworking iluid into a line 4d and a suitable turbine 46. Exhaust from theturbine i6 passes to a suitable radiator 48 for the release of excessheat energy. The exhaust from the radiator passes through a line Sil andback to the pump dll.

It should be noted that the working liquid is vaporized in the heatexchanger, and after passing through the turbine tle is again condensedin the radiator d8. The turbine 46 drives an electric generator 5d whichin turn provides the electrical energy for the electrical propulsionunit ld. The propulsion particles, which are accelerated rice out of theexhaust of the propulsion unit 14 by electrical means, comprise lithiumions which are supplied via the line 6l?. A valve 62 leading from theprimary circuit 16 expands a very minute portion of lithium and directsit to the electrical propulsion unit le, which for example, may be abombardment ion engine. The lithium is ionized in the ion engine ld andthe lithium ions are accelerated in the ion engine ld, thus providingspecific impulses in the range from 2,000 to 20,000 seconds. The majorportion of the lithium lremains in the primary circuit.

When short-duration impulsive thrust is desired, a relatively largeamount of lithium can be `directed from the primary circuit lo throughthe valve .ltl leading to the line 72. The line 72 leads to thecombustion chamber of the chemical rocket l2. The chemical rocket whenin loperation is also fed fuel and oxidizer (for example, hydrogen andfluorine) from respective containers or tanks '74 and 76. A suitablepump 73 and valve S0 are provided for the hydrogen which is fed throughthe line 32, while .a pump @d and valve S6 conduct the ow rof fluorineto the line Each of the lines '72, E2, and d4 conducts one of the threepropellants which comprise the combustion products for the rocket l2.

Thus, for very high thrust of short duration, the tripropellant rocketgives a very high, specific impulse. If further energy is desired, itmay be feasible to connect the hydrogen and fluorine `tanks in anysuitable manner to the nuclear reactor, as schematically illustrated lbythe dotted lines and 92. Thus, the chemical propellants would dl bepre-heated before being introduced into the rocket combustion chamber.

As a result of this invention, both high-thrust and lowthrust operationis readily achieved. The `fuel inventory for ferrying operations issubstantially reduced. ln addition, less cryogenic tanlsage is requiredthan for an ordinary hydrogen-lluorine propellant system. Of furtherimportance is the fact that a portion of the chemical rocket propellant,formerly charged off to payload, may now be used as electricalpropulsion fuel. Furthermore, the continual replenishment of lithium inthe closed-loop primary circuit will alleviate the problem of poisoningof the reactor coolant. ln addition, lithium has a low-neutronabsorptive quality which makes it acceptable to nuclear heating withoutcontamination. Finally, very high speciiic impulse is achieved in thechemical rocket, particularly if the nuclear reactor temperatures aresuch that the lithium is introduced in the vapor state.

Although one embodiment of this invention has been illustrated anddescribed herein, it Will be apparent that various changes may he madein the construction and arrangement of the various parts withoutdeparting from the scope of the novel concept.

What it is desired by Letters Patent is:

l. A compound propulsion unit including a rocket, means for supplying aplurality of propulsion ingredients to said rocket, an electricalpropulsion device and means for conducting one of said ingredients tosaid electrical propulsion device for acceleration therein.

2. A compound propulsion unit including a rocket, means for supplying aplurality of propulsion ingredients to said rocket, an electricalpropulsion device including means for accelerating propellant therein,and means for conducting one of said ingredients to said electricalpropulsion device for supplying the propellant to be accelerated.

3. A compound propulsion unit including a rocket, a plurality ofpropulsion ingredients including a source of lithium, means forsupplying said ingredients to said rocket, an electrical propulsiondevice, and means for conducting lithium from said source to saidelectrical propulsion device for acceleration therein.

4. A compound propulsion unit comprising a rocket device and anelectrical propulsion device, and means for supplying at least oneingredient as a common propulsive ingredient to both said devices.

5. A compound propulsion device including a rocket, sources of threepropulsive ingredients, means for conducting said ingredients to saidrocket for reaction therein, a nuclear heat source, means for convertingheat energy from said source into electrical energy, an electricalpropulsion device receiving electrical energy from said convertingmeans, and means conducting a relatively small portion of one of saidingredients to said electrical propulsion device for accelerationtherein.

6. A compound propulsion device including a rocket, sources of aplurality of propulsive ingredients including an element which isreadily ionized, means for conducting said ingredients to said rocketfor reaction therein, a heat source, means for converting heat energyfrom said source into electrical energy, an ion propulsion devicereceiving electrical energy from said converting means, and meansconducting a relatively small portion of said element to said ionpropulsion device for ionization and subsequent acceleration.

7. A compound propulsion device including a rocket, a plurality ofsources of different propulsive ingredients, means for conducting saidingredients to said rocket for reaction therein, a heat source, meansfor converting heat energy from said source into electrical energy, anelectrical propulsion device receiving electrical energy from saidconverting means, and means conductin'J a relatively small portion ofone of said ingredients to said propulsion device for use as apropellant.

8. A compound propulsion device including a rocket, a plurality ofsources of different propulsive ingredients, means for conductingselective amounts of said ingredients to said rocket for reactiontherein, a heat source, means for converting heat energy from saidsource into electrical energy, an electrical propulsion device receivingelectrical energy from said converting means, and means conducting arelatively small portion of one of said ingredients to said electricalpropulsion device for acceleration therein.

9. A compound propulsion system comprising a first cycle, said cyclehaving a first working fluid, a first path for circulating said firstworking fluid, a source or" heat for adding energy to said Workingfluid, a heat exchange unit receiving said working fluid, a second cycleincluding a second working fluid, means connecting said second cycle tosaid heat exchanger means to extract energy therefrom, means in saidsecond cycle for converting the energy from said second worldng fluidinto electrical energy, an electrical propulsion device receivingelectrical energy from said converting means, means for conductingWorking fluid from said first cycle to said electrical propulsiondevice, and a rocket receiving a portion of said first Working fluid foruse as thrust producing material.

10. A compound propulsion system comprising a first cycle, said cyclehaving a first working fluid which is readily ionized, a first path forcirculating said first Working fluid, a source of heat for adding energyto said worL ing fluid, a heat exchange unit receiving said Workingfluid, a second cycle including a second Working fluid, means connectingsaid second cycle to said heat exchange means to extract energytherefrom, means in said second cycle for converting the energy fromsaid second Working fluid into electrical energy, an ion propulsiondevice receiving electrical energy from said converting means, means forconducting Working fluid from said first cycle to said ion propulsiondevice for supplying the ions to be i accelerated, a rocket power plant,a plurality of sources of propulsive ingredients for said rocket andmeans for conducting at least a portion of said first Working fluid tosaid rocket for reaction with said ingredients.

1l. A compound propulsion system including a rocket, sources of threeingredients, means for conducting said ingredients for reaction in saidrocket, a first cycle receiving flow of one of said ingredients, asource heat in said first cycle for heating said one ingredient, meansfor extracting heat energy from said one ingredient, a second cycleincluding a Working fluid receiving energy from said extracting means,means for converting energy in said fluid into electrical energy, apropulsion device receiving electrical energy from said convertingmeans, and means conducting a portion of said one ingredient to saidpropulsion device to provide a propellant therefor.

l2. A compound propulsion system including a rocket, sources of threeingredients, means for conducting said ingredients for reaction in saidrocket, a first cycle receiving flow of one of said ingredients, asource of nuclear heat in said first cycle for heating said oneingredient,

leans for extracting heat energy from said one ingredient,

a second closed cycle including a Working fluid receiving energy fromsaid extracting means, means for converting energy in said iluid intoelectrical energy, an ion propulsion device receiving electrical energyfrom said converting means, and means conducting a portion of said oneingredient to said propulsion device for acceleration therein.

f3. A compound propulsion system including a rocket, sources ofpropulsion ingredients comprising hydrogen, iluorine and lithium, meansfor conducting said ingredients for reaction in said rocket, a firstcycle receiving flow of lithium from one of said sources, a source ofnuclear heat in said first cycle for heating said lithium, means forextracting heat energy from said heated lithium, a second cycleincluding a working fluid receiving energy from said extracting means,means for converting energy in said fluid into electrical energy, abombardment ion propulsion device receiving electrical energy from saidconverting means, and means conducting a portion of said lithium to saidpropulsion device for acceleration therein.

14. A compound propulsion system including a rocket, sources of threeingredients, means for conducting said ingredients for reaction in saidrocket, a first cycle receiving flow of one of said ingredients, asource heat in said first cycle for heating said one ingredient, meansfor extracting heat energy from said one ingredient, a second closedcycle including a Working fluid receiving energy from said extractingmeans, means for converting energy in said fluid into electrical energy,an electrical propulsion device receiving electrical energy from saidconverting means, and means conducting a portion of said one ingredientto said propulsion device for providing a thrustproducing material forsaid device.

References Cited in the file of this patent The lon Rocket Engine-aLikely Power Source for That Trip to Mars, by Donald L. Eschner, SAEJournal, August 1958, pages 30 to 32,

Dynamic Analysis of a Nuclear Rocket Engine System, by Bernard R. Felixand Richard J. Bohl, ARS Journal, November 1959, No. 11, vol. 29, pages853 to 862.

Space/Aeronautics, March 1960, pages -54.

1. A COMPOUND PROPULSION UNIT INCLUDING A ROCKET, MEANS FOR SUPPLYING APLURALITY OF PROPULSION INGREDIENTS